Sustained-release of Cyclosporin A pellets: preparation,in vitrorelease, pharmacokinetic studies andin vitro–in vivocorrelation in beagle dogs

The aim of this study was to develop Cyclosporin A (CsA) sustained-release pellets which could maintain CsA blood concentration within the therapeutic window throughout dosing interval and to investigate the in vitro-in vivo correlation (IVIVC) in beagle dogs. The CsA sustained-release pellets (CsA pellets) were prepared by a double coating method and characterized in vitro as well as in vivo. Consequently, the CsA pellets obtained were spherical in shape, with a desirable drug loading (7.18 ± 0.17 g/100 g), good stability and showed a sustained-release effect. The Cmax, Tmax and AUC0-24 of CsA pellets from the in vivo pharmacokinetics evaluation was 268.22 ± 15.99 ng/ml, 6 ± 0 h and 3205.00 ± 149.55 ng·h/ml, respectively. Compared with Neoral®, CsA pellets significantly prolonged the duration of action, reduced the peak blood concentration and could maintain a relatively high concentration level till 24 h. The relative bioavailability of CsA pellets was 125.68 ± 5.37% that of Neoral®. Moreover, there was a good correlation between the in vitro dissolution and in vivo absorption of the pellets. In conclusion, CsA pellets which could ensure a constant systemic blood concentration within the therapeutic window for 24 h were prepared successfully. Meanwhile, this formulation possessed a good IVIVC.